The overall objective of this research is to discover, study and establish novel control mechanisms for the regulation of anabolic and catabolic enzymes, and to analyze the physicochemical bases of enzyme-effector interactions. In this context we are investigating the structure and regulation of homoserine dehydrogenase and threonine dehydratases of several microorganisms. A separate aspect of our work involves genetic analysis of catabolic threonine dehydratase in order to elucidate the physiological and functional role of this inducible enzyme in coliaerogenes group of bacteria.